1. Technical Field
The present invention relates to a vehicle seat belt webbing pretensioner.
2. Description of the Prior Art
A typical vehicle seat belt system includes a length of belt webbing wound on a spool of a seat belt webbing retractor. The belt webbing is extensible about a vehicle occupant to restrain the occupant. The belt webbing spool rotates in a belt withdrawal direction as the occupant withdraws belt webbing from the retractor. A rewind spring is connected with the belt webbing spool and biases the belt webbing spool for rotation in an opposite belt retraction direction.
The seat belt webbing may sometimes become slack around the vehicle occupant. It is known to use a pretensioner to remove slack from the seat belt webbing in the event of a vehicle collision. The slack can be removed in different ways for example, by rotating the spool of the retractor in the belt retraction direction, by pulling on a buckle of the seat belt system, or by applying force to the belt webbing adjacent an anchor of the seat belt system.
It is known to use a pyrotechnic device, such as a gas generator, to provide fluid under pressure for tensioning the belt webbing. The fluid is used to rotate the spool in the belt retraction direction to tension the belt webbing, or to move a piston to pull on the belt webbing.